The research carried out under this grant covers three principal areas of cancer research: chemical carcinogenesis, viral carcinogenesis, and the regulation of expression in normal and cancer cells. The studies in chemical carcinogenesis are concerned with mechanisms involved in the initiation of cancer cells, factors involved in the promotion of initiated cells to clones of cells that can be recognized as tumors, and phenotypic differences among individual clones of altered cells and among individual gross tumors. The studies on viral carcinogenesis include an examiniation of the RNA tumor viruses and of two DNA viruses, Epstein-Barr virus and SV40. The studies on the regulation of gene expression are carried out with a variety of prokaryotic and eukaryotic systems and are directed toward a better understanding of the processes by which the expression of the genome is regulated and the implications of these models for an understanding of the malignant state.